[TypeCheckEffects] Fix AbstractFunction::getType to look through all levels of optional

A member and a parameter could be wrapped in an arbitrary number
of `Optional`, we need to look through all of them to get to the
underlying function type.

Resolves: rdar://151943924

Author: xedin

lib/Sema/TypeCheckEffects.cpp

@@ -386,7 +386,7 @@ class AbstractFunction {
   Type getType() const {
     switch (getKind()) {
     case Kind::Opaque:
-      return getOpaqueFunction()->getType()->lookThroughSingleOptionalType();
+      return getOpaqueFunction()->getType()->lookThroughAllOptionalTypes();
     case Kind::Function: {
       auto *AFD = getFunction();
       if (AFD->hasImplicitSelfDecl() && AppliedSelf)
@@ -395,8 +395,7 @@ class AbstractFunction {
     }
     case Kind::Closure: return getClosure()->getType();
     case Kind::Parameter:
-      return getParameter()->getInterfaceType()
-          ->lookThroughSingleOptionalType();
+      return getParameter()->getInterfaceType()->lookThroughAllOptionalTypes();
     }
     llvm_unreachable("bad kind");
   }

validation-test/Sema/type_checker_crashers_fixed/rdar151943924.swift

@@ -0,0 +1,18 @@
+// RUN: %target-typecheck-verify-swift
+
+@propertyWrapper
+struct Weak<Value> {
+    var wrappedValue: Value? { fatalError() }
+}
+
+struct WeakStorage<Item: Hashable> {
+    @Weak var action: ((Set<Item>) -> Void)??
+}
+
+final class Test {
+    var storage: WeakStorage<AnyHashable> = .init()
+
+    func test(items: Set<AnyHashable>) {
+        storage.action??(items)
+    }
+}